Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-03-17
2002-08-20
To, Doris H. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S456500, C455S436000, C455S432300
Reexamination Certificate
active
06438370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a cellular communication system, and more particularly to a location update method and an inter Core Network (CN) entity handover method, and further more particularly to a location update method and an inter-SGSN handover method in a 3
rd
Generation (3G) cellular system.
2. Description of Related Art
Cellular systems have had a direct effect on the lives of millions over the past few years. For the first time, people are able to make and receive phone calls without being tied to a specific location. Mobile phones, as part of the cellular systems, have allowed people to break the tie between location and access to communication. Mobile phones have also allowed people to reach another who is in move. With the development in cellular systems, people are allowed to reach another who is mobile in anywhere at anytime.
The first generation of mobile communication systems were born in the early 1980s. The marriage of radio and telephone technologies gave birth to mobile phones and triggered a turning point in telecommunications. Adding radio access to a telephone network meant that for the first time in history, the concept of a telephone being at a fixed point in the network was no longer valid. The benefits of being able to make and receive telephone calls anywhere had appeal to business people—the original market. In the first generation of cellular networks, analog wireless technology were used for the user connection (called the “air interface”). Every voice channel had its own narrow frequency band, using a technology called Frequency Division Multiple Access (FDMA).
However, as the demand for mobile phones grew and grew, regularly exceeding forecasts, it became obvious that the available radio spectrum would not be adequate to accommodate the expected numbers of mobile phone users. The digital technology became the solution to the problem. The answer lay in new digital wireless technologies that allow larger numbers of mobile subscribers to be supported within a given frequency allocation. Time Division Multiple Access (TDMA) technology is used in which a broader frequency channel is divided into intermittent time-slots, i.e. several calls share the same frequency channel at any one time. The digital technology also offered other important benefits. It provided better voice quality and improved security against unauthorized eavesdropping. Another technology, Code Division Multiple Access (CDMA) has also been developed subsequently to increase capacity.
The first and second generation mobile communication systems were mainly set to support voice communications, although today's mobile phones can also be used for data transfer at rates that are acceptable for relatively low-speed data applications such as sending and receiving of faxes and e-mail. However, these systems do not support high-speed data or video applications. The third generation mobile communication system is being developed to remove the bandwidth bottleneck and support a whole new range of voice, data, video, and multimedia services. For example, smart messaging is bringing Internet services to every mobile user's fingertips. As people become used to the freedom that mobile communications have provided, they will become more demanding about the information and services required to benefit their lives.
The demand by consumers all over the world for mobile communications service continues to expand at a rapid pace and will continue to do so for at least the next decade. To satisfy such demand, more and more innovative mobile telecommunications networks are being built in this growing industry.
In the 3
rd
generation cellular systems, many practical techniques are being developed over the past few years. The mobile telecommunication network comprises switching functions, service logic functions, database functions, and Mobility Management (MM) functions that enable subscribers to be mobile. These are some of the functions provided by Mobile Switching Centers (MSCs) for serving Circuit Switched (CS) connections, by Visitor Location Registers (VLR) for serving CS connections, or by other network entities, for example, Serving GPRS Support Node (SGSN) for Packet Switched (PS) connections (GPRS refers to General Packet Radio System).
Generally, the database in the Core Network (CN) keeps tracks of the location of Mobile Stations (MSs). In one case, the CN comprises both entities, MSC and SGSN, to implement such database. Each of the MSs can have a CS or PS connection service from the CN by sending radio signals to its Base Station (BS). Each of the BSs is controlled by a Radio Network Controller (RNC) which connects to the CN.
When a MS with an active connection moves from one area to another, a handover (also known as handoff) procedure is performed between the BSs During a handover procedure, a CN entity can operate in two different ways: one is called anchoring, and the other is called floating. In an anchoring procedure, the control of the MS remains in the first network entity where the connection between the MS and the CN was started, whereas in a floating procedure, the control of the MS is changed along with the move of the MS.
FIG. 6
shows an anchoring procedure.
FIG. 7
shows a floating procedure.
One of the problems in developing a 3
rd
generation cellular system is location update when a MS, e.g. with an active connection, moves from one area to another. This problem does not appear in a 2
nd
generation cellular system due to the fact that the 2
nd
generation cellular system does not use macro diversity and Iur-interface in the systems. In a conventional 2
nd
generation cellular system, e.g. GSM (Global System for Mobile communications), only one Base Station (BS) receives radio signals from a MS. Accordingly, when a MS moves from one area to another, the MS knows which BS controls the MS so that a location update can be performed by communicating between the MS and the CN via this BS. However, in a 3
rd
generation cellular system, to increase the capacity of the data transmission, a macro diversity and Iur-interface concept are introduced in the system. In particular, multiple Base Stations can receive radio signals from and to a MS, and due to the Iur-interface, the BSs are not necessarily connected to one Radio Network Controller (RNC). A Serving RNC (SRNC) informs the BS which MS is under its control and is connected to the CN entities in the CN. When a MS moves, the control to the MS may be changed from one RNC to the other RNC in a fashion that the MS may not be involved. As a result, when a MS moves from one area to another, the MS does not know when the SRNC is changed. If the MS sends a location update before the SRNC is changed, the location update may be sent to a wrong CN entity.
Another problem in a 3
rd
generation cellular systems is that during an active PS connection from a SGSN, a MS may move to an area where the SGSN should be changed. For instance, when a SRNC for a MS is changed, the new SRNC is connected to the new SGSN. In a 3
rd
generation cellular system, changing of a controlling SGSN needs to be executed in the CN because the MS does not know when it has entered in the new SGSN area and which RNC controls the MS due to the possible macro diversity and Iur-interface. In the existing 2
nd
generation cellular system, the new SGSN has to request from the old SGSN all information after the new SGSN receives a location update from the MS. During such a SGSN handover, all the radio related entities in RNCs, BSs, MSs, etc., have to be released. Thus, it is inefficient to perform an inter-SGSN handover.
Therefore, it can be seen that there is a need for an initiation scheme for location update of a MS in a 3
rd
generation cellular system. It can also be seen that there is a need for an inter-SGSN handover scheme in a 3
rd
generation cellular system.
SUMMARY OF THE INVENTION
To overcome the problems in the prior art described above, and to overcome other problems that will bec
Einola Heikki
Le Khiem
Rajaniemi Jaakko
Altera Law Group LLC
Nokia Telecommunications Oy
To Doris H.
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